Vue.set in plain array cause Cannot read properties of undefined (reading 'shallow') in 2.7.3

[gitpaladin]

Version

Reproduction link

codesandbox.io

Steps to reproduce

import Vue from "vue";

const a = [1, 2, 3];
Vue.set(a, 1, 100);   // Cannot read properties of undefined (reading 'shallow')

What is expected?

Set the array element by index.

What is actually happening?

Error occured.

---

Introduced in 2.7.3 with commit

360272b#diff-2e26135213b820cfd0eaba327405d14d405a4eee7d14a5c4acfcc2c84ef14692R244

[yyx990803]

Duplicate of #12632